That's great advice. Thanks, Andy! -Steve On Sun, Feb 17, 2013 at 2:12 PM, Andy Davies <dajdavies@gmail.com> wrote: > On 16 February 2013 05:25, Maciej Stachowiak <mjs@apple.com> wrote: > >> >> BTW as far as I know the best current nonblocking technique to phone home >> on unload is to create an <img> in your unload handler pointing to the ping >> URL, this will result in reliable delivery without blocking at least in IE >> and WebKit-based browsers. I've found it hard to convince even knowledgable >> web developers to use this technique or <a ping> over synchronous XHR, even >> sites that are otherwise willing to do Safari-specific optimizations. I am >> not sure why sync XHR in unload is so tantalizing. >> >> > I asked Phillip Tellis (creater of Boomerang) about this and his > experience is: (copied because he can't post to the list) > > "A beacon may be sent using a GET request via an Image object in a > listener for either the onunload,the onbeforeunload or the onpagehide > events. No browser blocks if this is sent via the onbeforeunload event, > however Opera does not support this event. Firefox is the only browser > that blocks for Image requests in the onunload event. > > Additionally, attaching a listener to the onunload event affects Page > Cache in most browsers, so one should avoid that in any event. > > The solution we've come up with for boomerang (a general purpose beaconing > solution primarily used for web performance beacons) is to attach a > listener to the beforeunload event and either the pagehide or unload, > depending on which is available (pagehide is checked first). The first of > these events to fire sends the beacon out and removes the listener from the > other. This has allowed us to fire beacons on every page unload without > affecting unload time and without beacon loss." > > Andy >
Received on Monday, 18 February 2013 19:40:13 UTC